NEw YorK AGRICULTURAL EXPERIMENT STATION. 143 
edge of this destructive disease. In estimating the value of this 
work it should be remembered that at the time it was done scarcely 
anything was known about bacterial diseases of plants. That bac- 
teria might be the cause of pear blight was first suggested by Prof. 
T. J. Burrill of the University of Illinois in 1878. Two years 
later he made inoculation experiments which showed that the dis- 
ease may be communicated from one pear tree to another by in- 
troducing into healthy tissue a bit of the bacteria-laden exudate 
from diseased twigs; also, that the disease may be artificially pro- 
duced in the apple and quince in the same manner. Little more 
than this was known about the pear disease when the investigations 
at the Station were begun in 1884; and the only other recognized 
bacterial plant disease was the hyacinth disease studied by Dr. 
Wakker, in Holland, in 1882.75 Undoubtedly, the illuminating 
pioneer work of Burrill and Arthur on pear blight has been an 
important factor in the rapid advances which have been made in 
our knowledge of bacterial plant diseases during the past twenty 
years. 
As regards the nature and results of the Station investigations 
on pear blight, they are best stated in Dr. Arthur’s own words. 
He says :116 “ The report of 1884 goes over the ground of Professor 
Burrill’s investigations, confirming his observations respecting the 
presence and activity of bacteria in connection with the disease, 
its infectious character as shown by inoculation, and the identity 
of pear blight and twig blight of the apple and quince. It was 
found that the disease could also be extended to various pomaceous 
fruits not tested by Professor Burrill, but could not be induced in 
plants of other orders. Inoculation in green fruit, taking up an 
original line of research, was found more certain of results than 
in the branches, and this with other things led to the belief that 
succulency has to do with the fullest development of the disease. 
Reasons are given for thinking that the bacteria accompanying the 
disease are the cause of it. The probable manner of the propaga- 
tion of the disease from tree to tree is outlined, and suggestions 
made as to remedies and preventions. In 1885 a rigid proof is 
given that the bacteria (Micrococcus amylovorus Bur.), which are 
always found accompanying the disease, are the actual cause of it. 
The discovery was made that the entrance of the bacteria into the 
™ Trans. Ill. Hort. Soc. for 1878:80 (1879). 
™ Bot. Centbl. 14:315 (1883). 
™° Rpt. 6:363 (1887). ‘ 
